Traditional energy harvesting systems are inefficient in mixing energy generated from multiple sources, because traditional energy harvesting systems do not prevent system startup cycle in situations of insufficient voltage generation from one or more of the multiple sources. Moreover, traditional energy harvesting systems typically use diode devices for energy mixing, resulting in substantially energy wasteful voltage drops. What is needed is an energy mixer that overcomes the problems of intermittent availability of all energy sources at the same time to avoid a full startup cycle triggered by energy source voltage output drop, and energy wasteful diode voltage drops.